1. Field of the Invention
The present invention is directed to an apparatus and method for applying liquid coatings to pellets in a flowing feed stream.
2. Description of Related Art
A continuing need has been identified for an apparatus which is capable of applying liquid coatings, such as liquid enzymes, to pelletized feed stock, in which the pellets are completely and evenly coated, and in which the apparatus is highly reliable, with low maintenance and low cost of ownership.
Enzymes are complex molecules which are naturally found in living organisms, and are used to speed up chemical reactions. In the animal feed industry, it has been found that, by adding a small amount of commercially available liquid enzyme to pelletized animal feed, complex structures within the feed that are not normally digested are, with the aid of the enzyme, made available for digestion. This allows for the reduction and/or elimination of certain feed additives, and also provides for higher nutrient yields.
It has also been found that lower cost corn/soy feed formulations, when combined with an appropriate enzyme addition, can provide similar nutritional value to more costly feed recipes which do not employ enzymes, and thus more economical primary feed ingredients can be used, resulting in lower production costs for the equivalent feed.
The enzyme phytase has also been successfully used in the broiler feed industry to liberate phosphorous normally not extracted through the digestive process. The use of phytase in the feed effects the reduction of phosphorous in the waste, thereby reducing potential environmental issues related to the disposal of that waste, and possible runoff into streams, lakes and tidal water systems.
Liquid enzyme formulations are readily available in concentrate form, and are normally diluted with water immediately prior to application. The apparatus and method of the present invention have been developed in order to achieve an accurate, highly repeatable means to apply liquid enzyme to pelletized animal feed, while reducing the overall dosing, and while achieving the desired minimal target activity within the pelletized product. This results in a minimized use of enzyme per quantity of feed pellets processed, and an attendant cost savings. The increased accuracy and high repeatability also provides the ability to formulate more economical feed recipes by being able to better predict and define the resulting nutrient value of the feed, such that it meets preset minimum nutrient value requirements for specific animals or specific ages of animals to be fed.
The present invention provides an apparatus and method for achieving highly accurate and highly repeatable application of liquid feed enzymes and other liquid-state products, such as hot fats, to feed products in pelletized form. The apparatus and method have broader applicability to liquid addition or liquid coating of any bulk material particulate flow.
The apparatus of the present invention is a gravity driven system, using a controlled material path in conjunction with a liquid delivery control system which delivers the liquid additive or coating material with a precision gauged by processing parameters such as the bulk material mass flow, liquid mass flow, the activity level of the liquid concentrate, and the desired target activity in the bulk material. This liquid delivery control is accomplished through the use of a control algorithm based in a microprocessor controller.
The bulk material delivery and handling equipment in the present apparatus includes a top flow conditioning section which performs the function of spreading the incoming material from its discharge stream shape, such that the material is distributed across the width of the apparatus. The feed conditioning section also agitates the bulk material, which is typically in pelletized form. The bulk material flows from the top conditioning section into a liquid application section in which, again, under the influence of gravity feed, the material is presented to a liquid spray which applies the liquid coating or additive to essentially one side (the side exposed to the spray) of the individual pellets or particles. The pellets or particles are then xe2x80x9cflippedxe2x80x9d in being moved to a second spray applicator section such that the previously unexposed sides of the pellets or particles are, for the most part, now exposed to a second liquid spray. The previously uncoated side is thus coated at this stage, with the result that the pellets or particles exit the apparatus having an essentially uniform coating applied to the entire surface thereof.